Sunday, September 20, 2009

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 201229
SWODY1
SPC AC 201226

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0726 AM CDT SUN SEP 20 2009

VALID 201300Z - 211200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
A PATTERN CHANGE WILL BEGIN TODAY AS THE STG POLAR JET STREAK DIGS
SEWD FROM THE NRN INTERMOUNTAIN W INTO THE CNTRL ROCKIES. THIS WILL
FORCE THE COMPLEX ARRAY OF SHORTWAVE TROUGHS LOCATED OVER THE SRN
PLNS AND MID-SOUTH NEWD TOWARD THE GRTLKS. AT THE SFC...INITIAL
CDFNT ASSOCD WITH THE WRN STATES UPR TROUGH WILL SURGE SEWD INTO THE
PLNS AND SRN ROCKIES BY TONIGHT AS A STRONGER CDFNT MOVES THROUGH
THE INTERMOUNTAIN W. MEANWHILE...DOWNSTREAM...WRMFNT SITUATED FROM
THE LWR OH VLY TO THE CAROLINAS WILL DEVELOP NWD INTO THE
MIDWEST/GRTLKS.

...CNTRL HIGH PLNS TO THE MID-MO RVR VLY...
12Z RAP/DNR SOUNDINGS SAMPLED A STOUT PRE-FRONTAL WARM NOSE AROUND
H85 OF 20-23 DEG C. THE EML AND ONLY MEAGER MOISTURE RETURN AHEAD
OF THE APCHG UPR TROUGH/SFC CDFNT WILL LIMIT DAYTIME SFC-BASED
CONVECTION OVER THE LWR PLNS. SCTD TSTMS WILL ACCOMPANY THE FRONT
ACROSS THE HIGHER TERRAIN OF WY/CO THROUGH THE DAY AND ISOLD DMGG
WINDS AND SMALL HAIL MAY ACCOMPANY THESE STORMS.

STRONGER LARGE SCALE HEIGHT FALLS AND MOISTENING ALONG NOSE OF AN
ACCELERATING SLY LLJ WILL WEAKEN CINH TONIGHT OVER THE LWR
PLNS/MID-MO VLY AND RESULT IN ELEVATED STORM FORMATION. STRONGER
UPDRAFTS MAY YIELD MARGINALLY SVR HAIL...BUT EFFECTIVE VERTICAL
SHEAR WILL GENERALLY BE LESS THAN 35 KTS...INDICATIVE OF MAINLY
MULTICELL STORMS WITH ONLY SMALL HAIL.

...OH/TN RVR VLYS SWD TO THE CNTRL GULF CST...
AIR MASS CHARACTERIZED BY PWATS OF AROUND TWO INCHES WILL SURGE NWD
THROUGH THE OH AND TN RVR VLYS TODAY AS SLY FLOW INCREASES AHEAD OF
THE WRN STATES UPR TROUGH. DESPITE POOR LAPSE RATES...POCKETS OF
HEATING WILL BOOST MLCAPES INTO THE 1000-1500 J/KG RANGE FROM THE
LWR OH VLY SWD INTO THE CNTRL GULF CST STATES. NEGLIGIBLE CINH AND
APCH OF A WEAK MID-LVL JET STREAK WILL CONTRIBUTE TO GRADUALLY
INCREASING DEEP MOIST CONVECTION THROUGH THIS MORNING. BOTH DEEP
AND LLVL SHEAR PROFILES WILL REMAIN MEAGER THROUGH THE
DAY...LIMITING A SUSTAINED ORGANIZED SVR STORM THREAT. A NON-ZERO
THREAT FOR ISOLD DMGG WET MICROBURSTS WILL EXIST WHERE STORMS
DEVELOP INVOF STRONGER LLVL CONVERGENCE/HEATING FROM WRN KY/TN SWD
INTO PARTS OF MS/AL.

..RACY/JEWELL.. 09/20/2009

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